Vacuum discharge gauge



Feb. 11, 1958 F. l.. Fox

vAcuuu DISCHARGE GAUQE original Filed Aug. 1'1, 1951 2 Sheets-Sheet 1 1:51 .lllll I I Y x .N m y m M S S TL n J mm m N/ H. s IM A D IW m g kn 2. n nl 0N Y 2. n uw tm QSE El mxzolwm n* W uw QN Il. ViniuHH n N 2. QN (2.

2 Sheets-Sheet 2 S QSE '-ATTORNE'Y United States Patent() VACUUM DISCHARGE GAUGE Frederick L. Fox, Pasadena, Calif., assignor, by mesne assignments, to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of California Original No. 2,758,232, dated August 7, 1956, Serial No.

242,259, August 17, 1951. Application for reissue August 5, 1957, Serial No. 677,189

Claims. (Cl. 313-7) Matter enclosed in heavy brackets :I appears in the original patent but forms no part of this reissue specilication; matter printed in italics indicates the additions made by reissue.

This invention relates to vacuum discharge gauges, and provides improved vacuum discharge gauges capable of operating over a wide range of pressures.

It has been proposed previously to'construct a vacuum discharge gauge having an anode electrode located adjacent to a pair of cathode electrodes, the anode and cathode electrodes being located within a glass enclosure which is coupled to a system containing a gas which is to be evacuated. A magnetic iield is provided between the cathode electrodes so as to cause the electrons to travel back and forth between the cathode electrodes before they are collected by the anode. When a high voltage is applied between the anode and the cathode electrodes of such a vacuum discharge gauge, the current which ows between the anode and the cathode electrodes varies with variations in the gas pressure within the chamber.

In order to provide a substantially linear response at low pressures, such a vacuum discharge gauge employs a large spacing between the anode and the two cathode electrodes. With such an arrangement, the current increases substantially linearly to its maximum value as the gas pressure within the chamber is increased from a predetermined minimum value, and then the current remains substantially constant until the gas pressure increases to a pressure which is less than atmospheric, whereupon the current decreases rapidly and is substantially zero at a pressure which is appreciably less than atmospheric.

lf such a vacuum discharge gauge were employed in an evacuated system in conjunction with a current-operated protection device for providing an alarm or a control means when the gas pressure in the evacuated system rises above a predetermined value, protection would be lost when the gas pressure in the evacuated system approached atmospheric pressure, because the current which ows through the vacuum discharge gauge is too small to operate the protection device. Moreover, were such a vacuum discharge gauge employed to measure gas pressure, an operator would have diiculty in determining whether the gauge was functioning within its substantially linear range, which occurs at low pressures, or within the pressure range near atmospheric pressure, for the electric current iewing through the gauge would be less than its maximum value for both of these pressure ranges.

In the apparatus of the present invention, a conductive housing is employed both to provide a Huid-tight chamber for enclosing an anode electrode and to provide a cathode electrode, and the operating range of the gauge is extended to atmospheric pressure by providing an auxiliary discharge gap which is connected between the anode electrode and the conductive housing. The spacing of the auxiliary gap is shorter than the spacing between the main anode and cathode electrodes, and it pro- ICC vides a smaller electron discharge space than that provided by the main anode and cathode electrodes.

The invention will be more fully understood from the following description and the drawings, wherein:

Fig. l is a sectional view of a preferred form of the apparatus of the invention;

Fig. 2 is a sectional view along line 2-2 in Fig. 1;

Fig. 3 is a sectional view along [ilne] line 3-3 in Fig. 2;

Fig. 4 is a curve which illustrates the operation of the invention; and

Fig. 5 shows one modification of the apparatus shown in Fig. l.

Referring to Figs. 1-3, a hollow conductive member 10 serves to provide a chamber for enclosing the electron discharge apparatus. The conductive member 10 should be composed of a non-magnetic material, for example, stainless steel. A pair of flanges 12, 14 are connected to the ends of the hollow member so as to provide a convenient means for attaching other apparatus to the member. An end plate 16 is connected to the ilange 12 by means of a pair of screws 18 and a guide pin 20. An annular ring 22, which is composed of a resilient material such as neoprene, is located in an annular groove 24 in the flange 12, and the ring serves to provide a vacuum seal between this flange 12 and the neighboring end plate.

A wire 26 in the form of an elongated loop, is supported by a conductor 28 so that the loop is centrally located within the chamber defined by the conductive member 10. A glass seal 30 serves to support the conductor 28, and the glass seal 30 is connected to the end plate 16 by means of a metallic member 32 and solder 33 which serve to provide a vacuum-tight seal between a shoulder 34 in the end plate 16 and the glass seal 30. A terminal 35 is connected to the conductor 28 so as to provide means for connecting a source of potential thereto.

A pair of mica washers 37 and 38 are located on the conductor 28 between the glass seal 30 and the junction between the conductor 28 and the wire 26. The washer 37 serves to close the circular aperture in the end plate 16 so as to prevent the waste products which are produced as a result of the elastic discharges within the member 10 from being deposited on the glass seal 30. Thus, the electrical insulation provided by the glass seal 30 is maintained substantially unimpaired even after extensive use of the discharge gauge.

An end plate 39 which is connected to the ange 14 by means of a pair of screws 40 is employed to couple the chamber defined by the member 10 to a system which is to be evacuated. A second annular ring 41, which is composed of a resilient material such as neoprene, is located in an annular groove 42 in the flange 14, and the ring 41 serves to provide a vacuum seal between the liange 14 and the end plate 39.

The system which is coupled to the chamber deiined by the member 10 by means of the end plate 39, is illustrated schematically in the drawings by the evacuated apparatus 43 and the vacuum pump 44.

A magnet 50 which is shaped like the letter C is located adjacent to the member 10 so that a magnetic field is provided in the chamber between the two parallel walls of the member 10, as shown in Fig. 3. The magnet 50 may be a permanent magnet or an electromagnet. The magnet 50 is disposed so that the magnetic ux lines are at right angles to the two parallel walls of the member 10 and to the plane of the loop formed by the wire 26, and the pole pieces of the magnet 50 are of approximately the same diameter as the transverse dimension of the loop defined by the wire 26.

various modifications may be made in the apparatus disclosed herein without departing from the scope of the invention. The auxiliary gap arrangement disclosed herein is not limited to use with the specific cathode and anode 26 arrangement shown in the drawings, but it may be employed in conjunction with any vacuum discharge gauge which provides an electron discharge path which is longer than the electron discharge path provided by the auxiliary gap.

I claim:

1. In a vacuum discharge gauge, the combination comprising a conductive member enclosing a portion of the space to be evacuated, a conductive electrode [in the form of a loop] extending within and electrically insulated and spaced from the co-nductive member to provi'de a rst electron discharge path in the space for measuring a p-redetermined range of pressures, [means for providing a magnetic eld in the space enclosed b-y the conductive member wherein the magnetic lines of ux are substantially normal to the plane of the lloop and a pair of spaced terminals comprising an end portion of the [loop] conductive electrode and a further conductor rigidly connected to the conductive member, said spaced terminals defining a gap located within the space to be evacuated and providing a second electron discharge path which is less fthan one-half the length of the tirst electron discharge path and which is adapted to pass current over a range of pressures higher than said predetermined range.

2. The apparatus of claim 1 wherein the conductive member is coupled to a system to be evacuated and wherein the spaced terminals comprise a pair of electrodes 1ocated within the system to be evacuated but outside the conductive member.

3. A vacuum gauge comprising a first conductive member defining a space to be evacuated, a second conductive member [in the form of the loop] extending within and electrically insulated and spaced from the first conductive member, the portion of the second conductive member which extends within the first conductive member being spaced substantially equidistant from a pair of opposed surfaces of the first conductive member, providing a rst electron path within the space to be evacuated for passing an increasing amount of current with increasing pressure over a predetermined range of pressures, and means afxed to one of the conductive members having an end portion which is separated from the other conductive member by a space which is less than one-half the distance between the opposed surfaces of the iirst conductive member, providing a second shorter electron path connected in shunt with the first electron path for passing current over a range of pressures greater than said predetermined range.

4. In a vacuum discharge gauge, the combination comprising a conductive member enclosing a portion of the space to be evacuated, a conductive electrode [in the form of a Iloop] extending Within and electricaliy insulated from the conductive member to provide a rst electron discharge path in the space for passing an increasing amount of current with increasing pres-sure over a predetermined range of pressures, [means for providing a magnetic Afield in the spaced enclosed by the conductive member with the magnetic lines of flux disposed approximately normal to the plane of the loop,] and means for providing a second electron discharge path located within the space to be evacuated with the second electron discharge path being connected in shunt with and having a shorter electron travel distance than the iirst electron discharge path for passing cur-rent over a range of pressures greater than said predetermined range, so that the conductive member and the conductive electrode may be energized as terminals to simultaneously energize both said rst and said second electron discharge paths.

5 In a vacuum discharge gauge, the combination comprising a conductive member, a conductive electrode, means for maintaining the space between the member and the electrode evacuated, the electrode being electrically insulated from the conductive member to` provide a first electron discharge path in the space for passing an im creasing amount of current with increasing pressure over a predetermined range of pressures, and means for providing a second electron discharge path located within the evacuated space with the second electron discharge path being connected in shunt with and having a shorter electron travel distance than the rst electron discharge path for passing current over a range of pressures greater than said predetermined range, so that the conductive member and the conductive electrode may be energized as terminals to simultaneously energize bath said first and said second' electro-n discharge paths.

References Cited in the le of this patent or the original patent UNITED STATES PATENTS 1,488,613 Pickard Apr. 1, 1924 2,490,468 Picard Dec. 6, 1949 2,497,213 Downing Feb. 14, 1950 2,497,823 Molloy Feb. 14, 1950 2,501,702 Varian Mar. 28, 1950 2,506,431 Perret et al. May 2, 1950 2,582,647 Morgan June 15, 1952 2,625,586 Lander Jan. 13, 1953 2,648,818 Cohen Aug. 11, 1953 FOREIGN PATENTS 630,885 Great Britain Oct. 24, 1949 

